What is Geographic Information Systems (GIS)?

what is geographic information systems gis
What is Geographic Information Systems (GIS)? GIS is a system that collects, displays, manages and analyzes geographic information. Let's explore all the aspects of a Geographic Information System a bit further.

Geographic Information Systems (GIS) Connects Geography with Data

Every day, millions of decisions are being powered by Geographic Information Systems (GIS)…

From pinpointing new store locations… to predicting climate change… to reporting power outages… to analyzing crime patterns.

You might be wondering: But why use GIS?

Because geographic problems require spatial thinking.

In a GIS, you connect data with geography. And you understand what belongs where. Because you don’t fully understand your data until you see how it relates to other things in a geographic context.

What is the definition for GIS?

Geographic Information Systems is a computer-based tool that analyzes, stores, manipulates and visualizes geographic information, usually in a map.

Never in the history of mankind have we had more pressing issues in need of a geospatial perspective. These global issues require pervasive, complex, location-based knowledge that can only come from a GIS.

Long story short:

Geographic Information Systems really comes down to just 4 simple ideas:

  • Create geographic data
  • Manage it.
  • Analyze it and…
  • Display it on a map.

These are the primordial functions of a GIS.

Visualize Data by Making Spreadsheets Come to Life

I think you’ll agree:

It’s REALLY hard to visualize the locations of latitudes and longitudes coordinates from a spreadsheet.

Latitude and longitude table
Attribute table

But when you add these positions on a map, it’s like magic to the reader.

Latitude and Longitude on a Map
Latitude and Longitude on a Map

Everyone knows that maps make geographic information easier to understand.

So what exactly do you need to make your spreadsheets (and other spatial information) come to life?

You need HARDWARE such as a GIS workstation. Actually, it could be anything from powerful servers to mobile phones. The CPU is your workhorse and data processing is the name of the game. In addition, GIS analysts often need dual monitors, boatloads of storage and crisp graphic processing cards.

Lastly, you need SOFTWARE. Really, the GIS software options out there seem endless. From ArcGIS, QGIS, GRASS GIS, SuperGIS, SAGA GIS to JUMP GIS… The range of GIS products to choose from can get a bit “ridiculous” at times. But this list of free GIS sofware will help.

READ MORE: Mapping Out the GIS Software Landscape

Drive Decision-Making in Real World Applications

Most people think GIS is only about “making maps”. But governments, businesses and people harness the power of GIS because of the insights of spatial analysis.

Before GIS, cartographers mapped out the land using paper maps. Over the years, we’ve seen a gradual shift away from paper maps. Instead, users build digital maps with computer-based spatial data.

And the more you think of it:

Some of the largest problems of our planet are best understood spatially. For example, climate change, natural disasters and population dynamics are all geographic in nature.

How do you solve problems in a GIS? The answer is through spatial analysis which understands relationships between spatial and attribute data.

READ MORE: 1000 GIS Applications & Uses – How GIS Is Changing the World

Spatial analysis examples:

Q: How much forest is in a city boundary or study area?
A: Run a clip on land cover classification. Sum the area of forest grid cells.

Clip Tool
Clip Tool
Q: How many endangered species are within a 1 mile proximity of a proposed mine?
A: Run a buffer. Calculate the number of species in the buffer.

Buffer Tool
Buffer Tool

READ MORE: 7 Basic GIS Processing Tools Every GIS Analyst Should Know

Manage Geospatial Data for Cost-Efficiency

There’s nothing more painful than drawing by-hand thousands of features on paper maps. But this is how it use to be.

Spatial analysis is impossible, querying is unimaginable and don’t even think about turning off a layer on a paper map.

GIS stores information about the real world as thematic layers. Of course, these layers are all linked by their geographic coordinates. As a result, we save cost because of greater efficiency in record-keeping and can make powerful spatial analysis with ease.

How does Geographic Information Systems capture real world features? Actually, GIS data is stored as rasters (grids) and vectors.

Rasters often look pixellated because of its square gridded look. They are store data in rows and columns (grid) and can be classified as discrete and continuous.

Continuous rasters are grid cells with gradual changing data. For example, digital elevation models (DEM) and temperature data are continuous raster data

Continuous raster
Continuous raster
Discrete rasters have distinct themes or categories. For example, land cover has discrete classes with clear boundaries. One grid cell represents a land cover class.

Discrete raster
Discrete raster

Vectors can be points, lines and polygons and are generally smooth, rounded features. For example, cities, fire hydrants, contours, roads, railways and administrative boundaries are often represented as vectors.


READ MORE: 10 Free GIS Data Sources: Best Global Raster and Vector Datasets

Build Your Career in Geomatics

GIS Data Layers - Geographic Information Systems
GIS Data Layers

If you thought a career in GIS meant only making maps, you’d be wrong.

From planning a pipeline to navigating ships, spatial problems need spatial thinkers. This is why Geographic Information Systems has expanded into countless other disciplines.

Tech-savvy employers expect the complete package of GIS skills. Now, GIS need skilled workers in multiple skill sets. For example, it’s helpful to learn programming, remote sensing, surveying, databases or web development.

  • Cartographers create maps. Actually, the origin of the job title comes from charta which means “tablet or leaf of paper” and graph ”to draw”
  • Database managers store and extract information from structured sets of geographic data.
  • Programmers write code and to automate redundant GIS processes. For example, GIS programming languages includes Python, SQL, C++, Visual Basic and JavaScript.
  • Remote sensing analysts use satellite or aerial imagery to map the Earth.
  • Spatial analysts manipulate, extract, locate and analyze geographic data.
  • Land surveyors measure the 3-dimensional coordinates on the land.

READ MORE: GIS Salary Expectations: Climb the GIS Career Ladder

GIS All Started by Mapping Cholera

When you look at an old map, it’s like you are traveling back in time.

A map not only shows geography, but paints a story of importance or struggle.

In 1854, spatial analysis began when cholera hit the city of London, England. Because no one knew how the disease started, British physician John Snow began mapping outbreak locations. But he also located roads, property boundaries and water lines.

When he added these features to a map, something interesting happened. He noticed how Cholera cases were commonly found along one of the water lines.

Cholera Map
John Snow’s Cholera Map

It was a major event connecting geography and public health safety. Not only was this the beginning of spatial analysis, it also marked the start epidemiology, the study of the spread of disease.

But it actually wasn’t until 1968 when GIS evolved into using computers:

Roger Tomlinson first coined the term “Geographic Information System” in his paper “A Geographic Information System for Regional Planning”. At this point in time, GIS truly became a computer-based tool for storing map data.

In 2014, Roger Tomlinson later passed away and will always be remembered as the “father of GIS”.

READ MORE: The Remarkable History of GIS

80% of Data is Geographic

It had been estimated that 80% of the informational needs of local government policy makers are related to geographic location.Robert Williams

GIS Percent 80% 20% location-based.

Unbelievably, GIS is being integrated in almost every discipline:

Amongst the group, environmentalists are the heaviest users. For example, climate change, groundwater studies and impact assessments are primarily GIS based. While agriculture maps out crop/soil types and use precision farming, in forestry, they use it for timber management, tracking deforestation and forest inventory.

More on the business side of things, GIS is used for site selection, consumer profiling and supply chain management. In real estate and land planning, GIS professionals use comparative analysis, location-based platforms and parcel-based planning. Also, it’s common to use GIS in the media to communicate stories with maps and target advertising campaigns.

Lastly, the military and defense are heavy GIS users pertaining to location intelligence, logistics management and spy satellites. Additionally, police use it for investigative analysis, in-vehicle mobile mapping, predictive policing. For public safety, GIS can visualize the spread of disease, disaster response and public health information.

This is just the tip of the iceberg. For example, archaeology, social work, transportation, education and water resources use GIS in some shape or form.

You’re looking at 20 professions who have adopted GIS technologies.

gis engineer

GIS and Remote Sensing in Wildfire Response

Back in August 2013, a wildfire hit Yosemite National Park, California. All said and done, experts estimated the extent of the fire to be 15 times the size of Manhattan island. Of all fires in California history, it was the fourth largest.

  • How was GIS used to respond to this wildfire?
  • And how did responders use Geographic Information Systems?
Step 1. Ask a question:
In this step, you ask a high-level question. This high-level question will guide you to obtaining the correct data, performing the analysis and examining the results.

As a land manager in Yosemite during a wildfire, how can we track the severity and effects of the wildfire? How can we monitor the recovery of the land?

Yosemite, California
Yosemite, California
Step 2. Capture data:
You can acquire satellite imagery and inspect the extent of the wildfire. Also, what other data could be useful such as roads, infrastructure and trails?

Yosemite National Park Pre-Wildfire
Yosemite National Park Pre-Wildfire (Landsat imagery courtesy of USGS/NASA Landsat)
Step 3. Analyze the situation:
Satellite data can display where vegetation is, which of course is fuel for the fire. If you can model fire behavior, you can map potential risks to communities and determine post-fire effects.

Yosemite National Park Wildfire
Post-wildfire satellite image false-colored. Fire appears bright red, vegetation is green, smoke is blue, clouds are white, and bare ground is tan-colored. (Landsat imagery courtesy of USGS/NASA Landsat)
Step 4. Respond to the problem:
In order to respond to the wildfire, communicate the best plan of attack to wildfire responders. After this wildfire, it’s beneficial to plan for future emergency by providing timely, accurate and relevant geospatial information as a data portal. Also, you can serve webmaps to fire managers with real-time fire perimeter data.

GIS Fire Perimeters
GIS Fire Perimeters

What Can GIS Do For You?

Geographic Information Systems answer important questions about location, patterns and trends.

For example:

  • Where are land features found? includes points, lines, polygons and grids. If you need to find the closest gas station, GIS can show you the way. Or if you want to find an optimal location, you may need traffic volumes, zoning information and demographics.
  • What geographical patterns exist? Ecologists who want to know suitable habitat for elk can gain a better understanding by using GPS collars and land cover.
  • What changes have occurred over a given period of time? Never have we’ve been able to understand climate change before thanks to GIS and remote sensing technology. Also, safety concerns can be better evaluated using GIS such as understanding terrain slope and the probability an avalanche can occur.
  • What are the spatial implications? If an electricity company wants to build a transmission line, how will this affect nearby homes, the environment and safety. Most environmental assessments use GIS to understand the landscape.

You might ask yourself:

Haven’t geographers been answering these questions for centuries?

Yes, they have. But in the most part, geographers have not been able to answer these questions very well because of the lack of data and processing.

Mapping the Future with Geographic Information Science

GIS Science

Paper maps will be completely obsolete in 10 years.

Bold statement? Definitely.

But take a step back and ask yourself:

How will GIS grow in upcoming years?

This is a question that is best understood with Geographic Information Science.

Geographic Information Science provides all the building blocks for Geographic Information Systems. It draws from computer science, mathematics, geography, statistics, cartography, and geodesy. GIScience incorporates the knowledge from these fields into Geographical Information Systems.

  • Geographic Information Systems connects what with the where.
  • Geographic Information Science discovers how.

In summary, Geography Information Science conceptualizes the collection, storage and analysis of spatial data in a Geographic Information System.

Why GIS is not going away anytime soon

geographic information systems infographic - what is gis
Click to enlarge infographic

Geographic Information Systems allows us to make better decisions using geography.

Analysis becomes simple.

Answers become clear.

Everyday GIS makes an impact on your life and you might not even realize. For example, your car uses GPS navigation and your job may depend on really accurate weather prediction. Overall, GIS helps us analyze the world because it best understands geography.

Cartographers, spatial analysts, surveyors, programmers and remote sensing analysts are GIS-based professions. According to a study awhile back, 80% of data is location-based.

When the natural resources community first started recording inventories on paper maps, it was quite a tedious process. But what did it really need?

A spatial database to record their observations. In addition, it needed a table to store attributes about the data.

What’s the bottom line?

Viewing and analyzing data geographically impacts our understanding of the world we live in.

A geographic information system (GIS) lets us visualize, question, analyze, and interpret data to understand relationships, patterns, and trends.

Williams, Robert (1987), Selling a geographical information system to government policy makers. Papers from the 1987 Annual Conference of the Urban and Regional Information Systems Association


  1. I described it all and lost it before it was posted. What I said was I hope to integrate GIS with Surveying since these should be two complementary tools. Maybe it’s just that those surveyors are “Out standing in their fields”. After 4 weeks, I’ve found that there is a lot more to it. “Gee. I thought it was going to be Simple” (GIS)

  2. Yes the infographic was created here. Please feel free to reuse if you’d like. If you can cite us somehow, that would be good… but you don’t have to

  3. This is so informative. I never felt sleepy reading. Everything is well stated. Thanks! I could use it in our capstone.

  4. I noticed a typo in the infographic. In the “Who Works” section, “remote sensing” is misspelled.

  5. Well, out of 105% are 80% geographical data and 25% are not… That is either interesting or magic.

  6. What programs are best for analyzing low income housing, where it exists, where it does not and what potential parcels might be available for creating more? I’m interested in housing the homeless as well as creating new housing for lower income people in California.

  7. You can usually obtain this type of data (zoning, parcels) from your local authority (state/county/city/town). It may be available on Esri Open Data (see below). The challenge for this is getting high quality data.

    For example, where are empty lots? If your local authority can’t provide you with data where land is developed… Alternatively, you can download data from OpenStreetMap (see below) where the mapping community has already digitised the globe to a certain level of completeness. However, you should validate with the latest imagery to make sure… Using the zoning and parcel data from your local authority group, you can overlay the OSM data that you have validated. Check for homeless shelters in OSM or Google Maps.

    Esri has some tapestry data where it characterizes neighborhoods. But it sounds like for your purpose, as you mention individual parcels, that it needs to be more detailed. Alternatively, you can use census data to help characterize areas.

    Best options for data: https://gisgeography.com/best-free-gis-data-sources-raster-vector/

    Look at #2 Esri open data, #4 OSM

    You can also potentially use real estate data for empty lots. In the past, this has been a challenging exercise because our landscape is changing every day.

  8. First, you’ll have to geocode the banks or get their lat/long coordinates. Next, you can create a heat map or some sort of visualization

  9. I am a mechanical engineer. Is this valuable for me to spend 2 years on an agreement in this GIS field? Please provide me a vision.

  10. Discovering GIS, I will be needing it to help in marking out my traditional land boundaries for my land so that I can provide to local authorities in applying for my land tittle. Please can you suggest to me what GIS software will best help me?

  11. Data in a geographic information system is referenced with locations (geographic coordinates). And using GIS software, you can visualize, edit, store and analyze that geographic data.

  12. Well. This is interesting.

    1. Kindly provide guidance on how best I can use a mobile phone to electronically collect and send elecronically to data base geocodes of TB patient residencies and their DOT service point in a city setting.

    2. Other than mobile phones what other gadgets can I use to collect this information.

  13. 1. There are better options nowadays than several years back. Collector for ArcGIS, QField for QGIS, Fulcrum, ArcPad

    2. Tablet, laptop, PDA

  14. I am an Hydrogeologist working with ministry of water resources. I am currently attached with a water laboratory where Physical, Chemical and Microbial analysis is being carried out by chemists and microbiologists. More than 500 water samples were being collected and data is being generated accordingly on each parameter on a quarterly basis. I am interested in GIS training. Which program on GIS will you recommend I start with for proper data interpretation and management in order to correlate the analytical results with geologic information of the water source. Thanks

  15. So informative and very interesting when I read GIS information but I coulden’t find any output of GIS so can provide some output of GIS?

  16. With all I am seeing here, I am really lacking in my knowledge of GIS practicality because it’s only theoritically based. I’ve got little knowledge on how to manipulate devices in analyzing geographical data.

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